Systems and processes for producing bio-fuels from lignocellulosic materials

ABSTRACT

A selective pyrolysis process for the production of bio-oils enriched in pyrolytic sugars and phenols and conversion of these compounds into second generation bio-fuels is disclosed herein. One embodiment of the process comprises pre-treating a biomass with superheated steam or gases in a selected range of temperatures, followed by fast pyrolysis using synthesis gas as a carrier, and a two-step condensation operation. The aqueous phase from the second condenser can then be reformed to produce hydrogen or can be gasified together with the charcoal to produce syngas.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/157,338, filed on Mar. 4, 2009, the disclosure of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to systems and processes for producing liquidfuels from lignocellulosic materials (e.g., agricultural and forestryresidues and energy crops).

BACKGROUND

Biomass is an attractive feedstock to offset fossil fuels because it iscarbon neutral (or negative), renewable, and may be domesticallyproduced. One conversion platform uses a thermo-chemical process(commonly referred to as “pyrolysis”) to convert biomass into bio-oil.Bio-oils are similar in appearance and color as crude oil though bio-oilcontains considerably more oxygenated and functional compounds.

Although bio-oil can be used directly for stationary diesel engines,bio-oil may be too corrosive and viscous as a transport fuel. There ishowever great potential to use bio-oil as a feedstock for centralizedrefineries to produce chemical products and/or transportation fuels.However, several technical challenges exist for the utilization ofbio-oil as a feedstock. First, bio-oils are highly acidic and may becorrosive to pipes and storage vessels. Secondly, bio-oils can beunstable when stored for prolonged periods of time. Third, bio-oilstypically contain a wide variety of molecules including a substantialamount of small molecules, which are difficult to upgrade. Accordingly,several improvements in converting biomass to bio-oils are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a system for convertingbiomass into bio-oils in accordance with embodiments of the technology.

FIG. 2 is a schematic diagram illustrating a system for performingbio-oil refining in accordance with embodiments of the technology.

FIGS. 3A and 3B are schematic diagrams illustrating a reactor inaccordance with embodiments of the technology.

FIG. 4 is a graph showing ratios of peaks in Py-GC/MS chromatogramassigned to levoglucosan and to hydroxyacetaldehyde in accordance withembodiments of the technology.

FIG. 5 shows the changes of levoglucosan/furfural ratios as a functionof pyrolysis temperature in accordance with embodiments of thetechnology.

FIGS. 6 and 7 show the ratio of levoglucosan and other products ofoxidation reactions in accordance with embodiments of the technology.

FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a function ofpretreatment temperature in accordance with embodiments of thetechnology.

FIG. 9 shows levoglucosan/hydroxyacetaldehyde ratios as a function ofpyrolysis temperature in accordance with embodiments of the technology.

FIG. 10 shows a glucose content as a function of fermentation time inaccordance with embodiments of the technology.

FIG. 11 shows a rate of microbial growth in solutions derived frombio-oils and in control solutions produced with glucose in accordancewith embodiments of the technology.

FIG. 12 shows ethanol concentration as a function of fermentation timein accordance with embodiments of the technology.

FIG. 13 shows sugar consumption and production of fatty acids as afunction of fermentation time in accordance with embodiments of thetechnology.

DETAILED DESCRIPTION

Specific details of several embodiments of the disclosure are describedbelow with reference to systems and processes to selectively convertlignocellulosic materials into a bio-oil that is rich in anhydrosugars(e.g., levoglucosan and cellobiosan) and phenols as well as the furtherconversion of the anhydrosugars to ethanol and/or lipids. The term“lignocellulosic materials” generally refers to materials containingcellulose, hemicelluloses, and lignin. Examples of lignocellulosicmaterials include wood chips, straws, grasses, corn stover, corn husks,weeds, aquatic plants, hay, paper, paper products, recycled paper and/orpaper products, and other cellulose containing biological materials ormaterials of biological origin. Several embodiments can haveconfigurations, components, or procedures different than those describedin this section, and other embodiments may eliminate particularcomponents or procedures. A person of ordinary skill in the relevantart, therefore, may understand that the technology may have otherembodiments with additional elements, and/or may have other embodimentswithout several of the features shown and described below with referenceto FIGS. 1-13.

FIG. 1 is a schematic flow diagram illustrating a system 100 forconverting biomass into bio-oils in accordance with embodiments of thedisclosure. As shown in FIG. 1, the system 100 includes a drier 102, atorrefaction unit (with an optional grinder) 104, a pyrolysis reactor106, a first condenser 108, a second condenser 110, and a combustor 112operatively coupled in series. The system 100 also includes anevaporator 114, a steam reformer 116, and a gasification reactor 118operatively coupled to one another as well as to the pyrolysis reactor106 and the second condenser 110. Even though only particular componentsare shown in FIG. 1, other embodiments of the system 100 can alsoinclude washers, decanters, filters, and/or other suitable components inaddition to or in lieu of the foregoing components of the system 100.

The dryer 102 can include a direct-contact dryer, an indirect-contactdryer, and/or other suitable types of dryer. In the illustratedembodiment, the dryer 102 includes a direct-contact dryer configured toreceive and contact the biomass 1 with a hot combustion gas 6 from thecombustor 112. The exhaust from the dryer 102 is vented to atmosphere.In other embodiments, the dryer 102 can also be coupled to an optionalhot gas source (e.g., hot air, not shown) for start-up, supplementingthe hot combustion gas 6, and/or other suitable purposes. After drying,the dryer 102 provides a dried biomass 2 to the torrefaction unit 104.In further embodiments, the dryer 102 and the torrefaction unit 104 canbe integrated in a single unit (not shown).

The torrefaction unit 104 can be configured to pre-treat the driedbiomass 2 before subjecting the dried biomass 2 to pyrolysis. Thetorrefaction unit 104 can include any vessel capable of controllablyheating the dried biomass 2 to a desired temperature. Optionally, thetorrefaction unit 104 can also include a grinder and/or other suitablecomponents to reduce the size of the dried biomass 2. For example, inone embodiment, the torrefaction unit 104 can include an auger reactorconfigured to controllably heat the dried biomass 2 while reducing thesize of the dried biomass 2, as described in more detail below withreference to FIG. 4. In other embodiments, the torrefaction unit 104 mayalso use a synthesis gas 16 from the reformer 116 as a carrier gas forthe pretreatment reactions.

The pyrolysis reactor 106 can include a fluidized bed, a fixed bed, anablative reactor, vacuum pyrolysis reactor, auger pyrolysis reactor,and/or other suitable types of pyrolysis reactors. In one embodiment,the pyrolysis reactor 106 can include embodiments of the auger reactorshown in FIG. 3. In other embodiments, the pyrolysis reactor 106 caninclude other types of reaction vessels. Even though the torrefactionunit 104 and the pyrolysis reactor 106 are shown as separate componentsin FIG. 1, in certain embodiments, the torrefaction unit 104 and thepyrolysis reactor 106 can be combined into a single component. Infurther embodiments, a single component (e.g., the reactor of FIG. 3)may perform the function of both the torrefaction unit 104 and thepyrolysis reactor 106. As a result, the torrefaction unit 104 and thepyrolysis reactor 106 may be integrated into a single unit.

The first and second condensers 108 and 110, the boiler 114, and thereformer 116 can individually include a plate-and-frame, tube-and-shell,brazed aluminum, and/or other types of heat exchanger. In oneembodiment, the first condenser 108 can be an empty scrubber. In otherembodiments, the first condenser 108 can operate in other suitablefashion. Even though the first and second condensers 108 and 110 areshown as separate components in FIG. 1, in certain embodiments, thefirst and second condensers 108 and 110 may be combined into a singleheat exchanger. In further embodiments, one of the first and second heatexchangers 108 and 110 may be omitted.

The combustor 112 can be configured to react a combustible gas with airand/or oxygen to produce electrical, heat, and/or other forms of energy.In the illustrated embodiment, the combustor 112 includes a gas turbinecoupled to an electrical generator. In other embodiments, the combustor112 can also include a gasoline engine, a diesel engine, a ramjet,and/or other suitable combustion components. In further embodiments, thecombustor 112 may be omitted.

The gasification reactor 118 can be configured to convert a carbonaceousmaterial into a combination of hydrogen, carbon monoxide, carbondioxide, and/or other suitable gaseous components. The gasificationreactor 118 can include a counter-current fixed bed gasifier, aco-current fixed bed gasifier, a fluidized bed reactor, an entrainedflow gasifier, and/or other suitable types of gasifier.

In operation, the biomass 1 is provided to drier 102. The drier 102dries the biomass 1 with, for example, the combustion gas 6 from thecombustor 112. The dried biomass 2 then enters the torrefaction unit 104to be pre-treated prior to pyrolysis. In certain embodiments, thetorrefaction unit 104 heats the dried biomass 2 to a desired temperature(e.g., about 200° C. to about 300° C.) for a treatment period (e.g., 3min to about 10 hours) with a portion of the synthetic gas 15 from thereformer 116 as a carrier gas.

The pre-treatment temperature and time may depend on each other. Forexample, a high pre-treatment temperature may require a short treatmenttime and vice versa. Without being bound by theory, it is believed thatpre-treating the biomass 1 in the torrefaction unit 104 can (1) removeat least part of the hemicellulose and acetic acid from the solidmatrix; (2) reduce the degree of polymerization of cellulose andincrease crystallinity of the cellulose; (3) de-polymerize at least partof the lignin; and (4) weaken biomass fibrous structure for ease ofgrinding.

The pre-treated biomass is then provided to the pyrolysis reactor 106 inwhich the biomass is thermally converted at temperatures between 400 and500° C. into a vapor phase pyrolysis product 3 and bio-char 8. Incertain embodiments, the pre-treated biomass provided to the pyrolysisreactor 106 may contain additives (e.g., H₂SO₄, (NH₄)₂HPO₄ and(NH₄)₂SO₄) at concentrations of about 0.1 mass % or other suitableconcentration values. The additional of such additives are believed toenhance the production of anhydrosugars from biomass. In otherembodiments, the pyrolysis reactor 106 may contain other suitablecompositions.

In the illustrated embodiment, the first and second condensers 108 and110 may then condense the pyrolysis product 3 with ambient air 17(and/or other suitable coolant) to separate and collect differentfractions from the pyrolysis product 3 and produce heated air streams 18and 19, which is provided to the combustor 112. In other embodiments,the first and second condensers 108 and 110 may both cool the pyrolysisproduct 3 with ambient air.

The temperature in the first condenser 108 can be controlled to separateheavier compounds (e.g., phenols and sugars) from light compounds (e.g.,acetic and formic acid). A bio-oil 9 can be separated via solventextraction (e.g., with ethyl acetate) and/or other suitable techniquesto produce a stream rich in phenols and pyrolytic sugars. A firstfraction of the bio-oil 9, which is rich in sugar can then behydrolyzed, detoxified and fermented to produce ethanol and/or can besubject to other types of suitable processing to produce otherhydrocarbons. A second fraction of the bio-oil 9, which is rich inphenols can be converted into green gasoline via hydro-treatment and/orother suitable processes, as described in more detail below withreference to FIG. 2.

The second condenser 110 can then receive an output stream 4 from thefirst condenser 106 and collect an aqueous stream 10 from the pyrolysisproduct 3. The aqueous stream 10 is then supplied to the reformer 116via the boiler 114 to produce a synthetic gas 20. The synthetic gas 20is then provided to the combustor 112 for conversion into electricityand/or other forms of energy. Optionally, the aqueous stream 10 can begasified with the bio-char 8. The gasification reactor 118 can convertat least a portion of the bio-char 8 into a synthetic gas 14 provided tothe reformer 116 and output the rest of the bio-char 8 as char and ash.In other embodiments, the bio-char 8 may be provided to the combustor112 and/or otherwise processed. In further embodiments, the bio-char 8may form a final product of the process.

Several embodiments of the technology utilize pretreatment with specifictemperatures to produce the bio-oil 9 that is more enriched in sugars,less corrosive, more stable than conventional bio-oils. Without beingbound by theory, it is believed that biomass degradation via pyrolysismay be classified into three general categories: de-polymerization,fragmentation, and polycondensation. Depolymerization reactions arebelieved to yield primarily monomers that are greater than five carbons.Such monomers may be either carbohydrodrate (fromcellulose/hemicellulose) or aromatic (from lignin). Fragmentationreactions are believed to lead to the formation of small molecules thatare typically smaller than five carbons. Poly-condensation reactions arebelieved to result in the formation of charcoal. Pyrolysis reactors canreduce the formation of char by having very high heating rates which mayreduce the time the material is in the temperature range of 270-350° C.in which dehydratation and crosslinking reactions are favored.

Several embodiments of the system 100 can alter the structuralproperties of the biomass 1 for improving the selectivity to favordepolymerization reactions and improve the bio-oil quality producedduring pyrolysis. Several factors are believed to influence whetherdegradation proceeds via fragmentation or de-polymerization reactions.The presence of alkaline is believed to strongly catalyze fragmentationreactions. Other factors such as degree of polymerization,crystallinity, and the interactions lignin/cellulose are also factorsthat can be adjusted to improve reaction selectivity towardde-polymerization (formation of precursors of transportation fuels).Thus, by increasing the crystallinity and reducing the degree ofpolymerization via heating in the temperature range of about 200° C. toabout 300° C. (in the presence or absence of steam), the reactionselectivity to de-polymerization may be improved.

Several embodiments of the systems and processes can also havesubstantial energy savings as a result of pretreatment for grindingoperations. The pretreatment not only removes components of thematerial, it may also attenuate the physical integrity and reduce theenergy required to reduce particle sizes to what is required for thepyrolysis reactor. It should be noted that grinding can contribute to asmuch as 10% of the total energy in the biomass.

FIG. 2 is a schematic diagram illustrating a process 200 for performingbio-oil refining in accordance with embodiments of the disclosure. Asshown in FIG. 2, the process 200 can include separating a phenolicfraction from an aqueous fraction in the bio-oil 9. Techniques suitablefor this separation can include liquid-liquid extraction with water, anorganic solvent, and/or other suitable materials. The phenolic fractioncan then be hydro-treated with hydrogen to produce green gasoline. Theaqueous fraction can be (1) hydro-treated under high pressure to producegreen diesel; (2) hydrolyzed, neutralized, and detoxified to producelipids; and/or (3) hydrolyzed, neutralized, detoxified, and fermented toproduce alcohol.

FIG. 3A is a schematic diagram illustrating an reactor 300 in accordancewith embodiments of the technology. As shown in FIG. 3A, the reactor 300includes a feeder 302 coupled to a treatment zone 304 having a first end303 a and a second end 303 b. The feeder 302 can include a screw pumpand/or other suitable material moving components. The treatment zone 30can include a generally helical auger (or screw) 307 and/or othersuitable structures inside a housing 305 and a motor 320 operativelycoupled to the auger 320.

The reactor 300 also includes a heat exchanger 306 and a furnace 308 onthe housing 305 and a power supply/controller 310 operatively coupled tothe furnace 308. The reactor 300 further includes a solid container 312and a condenser 314 proximate to the second end 303 b of the treatmentzone 304. Optionally, the reactor 300 includes a plurality of coolingtraps 316 coupled to the condenser 314 for collecting condensedmaterials.

In operation, the feeder 302 forces biomass (shown as separate spheresin FIG. 3A for illustration purposes) to enter the treatment zone 304via the first end 303 a along with an optional carrier gas. The heatexchanger 306 and the furnace 308 then heats the biomass to a desiredtemperature while the auger 307 moves the biomass toward the second end303 b and reduces the size of the biomass. Solid portions of the biomassare then collected at the solid container 312 while volatile portionsare collected at the condenser 314 and/or the cooling traps 316.

A single reactor 300 may be used for both pre-treating and pyrolysis ofthe biomass. For example, the biomass may be processed in the reactor300 at a first temperature (e.g., about 200° C. to about 300° C.). Thecollected solid portions may then be returned to the feeder 302 to beprovided to the auger 304 and processed at a second temperature (e.g.,about 500° C. to about 600° C.).

In other embodiments, as shown in FIG. 3B, the reactor 300 may includemore than one treatment zones (e.g., by having more than one furnaces)such that the pre-treatment and pyrolysis operations may be performed ina continuous fashion. Several components shown in FIG. 3B are generallysimilar in structure and function as those shown in FIG. 3A. As aresult, common acts and structures are identified by the same referencenumbers.

As shown in FIG. 3B, the reactor 300 can include a first treatment zone304 a coupled to a second treatment zone 304 b. The first treatment zone304 a can include a first auger (or screw) 307 a inside a first housing305 a having a first end 303 a and a second end 303 b. The first auger307 a can be operatively coupled to a first motor 320 a. The firsttreatment zone 304 a also includes a first furnace 308 a proximate tothe first housing 305 a and operatively coupled to a first powersupply/controller 310 a. The first treatment zone 304 a also includes acarrier gas inlet 324 a and a carrier gas outlet 324 b in fluidcommunication with the auger 307 a.

Optionally, the first treatment zone 304 a can also include a grinder322 and/or other suitable components configured to reduce a physicalsize of the biomass in the first treatment zone 304 a. In theillustrated embodiment, the grinder 322 is proximate to the second end303 b of the first treatment zone. In other embodiments, the grinder 322may be at other locations of the first treatment zone or may be omitted.

The second treatment zone 304 b can have generally similar components asthe first treatment zone 304 a. For example, the second treatment zone304 b can include a second auger 307 b in a second housing 305 b andoperatively coupled to a second motor 320 b. The second treatment zone304 b can also include a second furnace 308 b proximate to the secondhousing 305 b and operatively coupled to a second powersupply/controller 310 b.

In operation, the feeder 302 forces biomass to enter the first treatmentzone 304 a via the first end 303 a along with an optional carrier gasvia the carrier inlet 324 a. The heat exchanger 306 and the firstfurnace 308 a then heats the biomass to a first temperature (e.g., about200° C. to about 300° C.) while the auger 307 moves the biomass towardthe second end 303 b. The optional grinder 322 can then reduce thebiomass from the first treatment zone 304 a to particle sizes less thanabout 2 mm before the biomass is provided to the second treatment zone304 b. The second furnace 308 b can then heat the biomass to a secondtemperature (e.g., about 500° C. to about 600° C.) to thermally convertthe biomass via pyrolysis. Solid portions of the biomass are thencollected at the solid container 312 while volatile portions arecollected at the condenser 314 and/or the cooling traps 316.

Even though embodiments of the reactor 300 are shown in FIGS. 3A and 3Bas being carried by a cart, in other embodiments, various components ofthe reactor 300 may be separately and/or fixedly installed. In otherembodiments, the reactor 300 may utilize other components for conveyingand/or reducing size of the biomass. For example, in certainembodiments, at least one of the first and second augers 307 a and 307 bmay be omitted in the reactor 300 shown in FIG. 3B. Instead, the reactor300 may carry the biomass through the treatment zones 304 a and 304 bpneumatically, hydraulically, and/or via other suitable means. Infurther embodiments, the biomass may be treated in at least one of thefirst and second treatment zones 304 a and 304 b in a batch mode. In yetfurther embodiments, the reactor 300 can include three, four, and/orother suitable number of treatment zones with similar or differentconfigurations.

EXAMPLES

Tests were conducted to understand the effect of torrefaction conditions(temperature and presence of oxygen) and pyrolysis temperatures on theselectivity of pyrolysis reactions towards the production ofanhydrosugars were carried out in our Py-GC/MS. The pretreatment wasperformed at temperatures ranging from 200 to 320° C. Pyrolysis testswere conducted at temperatures between 350 and 550° C. The tests werecarried out with Avicel (crystalline cellulose with low degree ofpolymerization), α-cellulose (a blend of cellulose and hemicellulose),wheat straw and the woody fraction of Douglas Fir (containing cellulose,hemicelluloses and lignin). Before conducting the Py-GC/MS studies, thealkalines in all the samples were removed with hot water (at 120° C.).

The Py-GC/MS tests were carried using a CDS pyro-probe 5000 connectedin-line to an Agilent GC/MS. Samples were loaded into a quartz tube andgently packed with quartz wool prior to pyrolysis. The samples were keptfor 3 minutes at the pretreatment temperature before the oventemperature was reduced to 210° C. The samples were kept in theseconditions for 1 minute. Samples were pyrolysed by near instantaneousheating to the final temperature and held at this temperature for 3minutes.

The GC/MS inlet temperature was maintained at 250° C. and the resultingpyrolysis vapors were separated by means of a 30 m×0.25 μm innerdiameter column. The column was heated at 3° C./min from 40 to 280° C.The gas was then sent into a mass spectrometer and the spectra of themost important peaks were compared to an NBS mass spectra library toestablish the identity of each compound.

FIG. 4 shows the ratio of the area of the peaks in the Py-GC/MSchromatogram assigned to levoglucosan (a product of cellulosedepolymerization reactions) and to hydroxyacetaldehyde (a product ofcellulose fragmentation reactions). This ratio can be used as an indexof the selectivity of thermochemical reactions towards the production ofanhydrosugars. FIG. 4 shows that a mild torrefaction in the range oftemperature between 200 and 320° C. can enhance the production oflevoglucosan for α-cellulose, wheat straw and the wood fraction ofDouglas Fir.

The presence of oxygen during torrefaction had a positive effect onwheat straw. For all the other biomasses, the presence of oxygen duringpretreatment is detrimental to the yield of sugar obtained. In the caseof Wheat Straw the highest selectivity towards the production ofanhydrosugars was obtained for samples pretreated at temperature over270° C. in the presence of oxygen. For Douglas Fir the best results wereachieved for samples pretreated in the absence of oxygen at temperaturesover 230° C. It is noteworthy that a drastic increase in the selectivitytowards the production of levoglucosan was also observed when theDouglas Fir wood was heated in the presence of oxygen at temperaturesover 310° C.

FIG. 5 shows the changes of levoglucosan/furfural ratios as a functionof pyrolysis temperature in accordance with embodiments of thetechnology. The pretreatment temperature does not have any effect on theLevoglucosan/furfural ratios for the Avicel. This result suggests thatAvicel was not dehydrated in the pretreatment conditions tested. In thecase of α-cellulose, an increase in the levoglucosan/furfural ratio wasobserved as the pretreatment temperature increases. The presence ofoxygen during pretreatment of α-cellulose and Avicel causes a reductionin the levogluocan/Furfural ratio for most of the materials but not forthe wheat straw. The conditions improving the ratiolevoglucosan/furfural are very similar to those improving the ratiolevoglucosan/hydroxyacetaldehyde.

FIGS. 6 and 7 show the ratio of levoglucosan and other products ofoxidation reactions in accordance with embodiments of the technology.With the exception of wheat straw, the shapes of the curves describingthe evolution of the levoglucosan/carbon dioxide and levoglucosan/aceticacid ratio are similar to those shown in FIGS. 4 and 5. For the wheatstraw there is a maximum for samples pretreated in the presence ofoxygen. This maximum could indicate the temperature at which oxidationreactions responsible for the formation of CO₂ and acetic acidaccelerate.

FIG. 8 shows levoglucosan/2-methoxy phenol ratios as a function ofpretreatment temperature. The conditions improving this ratio weresimilar to those improving the levoglucosan/CO2 and levoglucosan/aceticacid ratios. But, pre-treating biomass in the presence of oxygenconsiderably increases the production of mono-phenols due to theoxidation of lignin linkages. According to our results thelevoglucosan/2-methoxy phenol ratio can be improved if the wheat strawis pretreated at a 270° C. in the presence of oxygen. The presence ofoxygen was detrimental for the Douglas Fir.

The effect of pyrolysis temperatures on the selectivity ofthermochemical reactions towards the production of levoglucosan inunpretreated samples is shown in FIG. 9. The results indicate that asthe pyrolysis temperature increases the fragmentation reactionsresponsible for the formation of hydroxyacetaldehyde are favored overthe depolymerization reactions responsible for the formation ofanhydrosugars. Although this behavior was observed for all the samples,the effect of temperature was more pronounced for the Avicel and for theα-cellulose. Materials containing lignin show a much less pronouncedeffect.

Tests on auger pyrolysis were also conducted. Douglas Fir wood waspre-treated at select conditions identified by Py-GC/MS and was subjectto pyrolysis in the Auger Pyrolysis reactor built at Washington StateUniversity (generally similar to that shown in FIG. 3A). During testing,200 g of Douglas Fir samples were added into 3 L of deionized water. Thebiomass and the water were heated in an autoclave (Consolidated Stills &Sterilizers) at 120° C. for 20 min.

The water and the solid were separated by filtration. The solid wasdried overnight at 105° C. For every 200 g of biomass 175 g ofpre-treated samples were obtained (87.5 mass %). These samples werefurther subject to a mild torrefaction in the same Auger reactor butusing lower wall temperatures (e.g., 270° C.). The reactor was operatedunder a nitrogen atmosphere (flow rate of nitrogen: 3 l/min) and thebiomass particles were conveyed through the Auger at 5.2 rpm(Pretreatment time: 2.5 minutes).

Pyrolysis tests on the pre-treated samples were carried out in the sameAuger Pyrolysis reactor. The reaction conditions were the following:Auger speed: 13 rpm (residence time of particles in the reactor: 1minute), hopper feeding rate: 43.6 rpm, pressure inside the reactor: 1atm., carrier gas: N2, flow rate: 10 l/min, temperature in the wall ofthe reactor: 500° C., post-oven temperature 420° C.; estimated heatingrate: (4-7° C./s or 240-420° C./min). Although the heating ratesachieved are lower than the 10-1000° C./s needed for fast pyrolysisreactors it is still faster than the 10° C./min typically reported forslow pyrolysis. The yield of products obtained with Douglas Fir asreceived and after hot water and thermal pretreatment at 270° C. for 3minutes are shown in Table 1. The oil produced in our system is a singlephase oil very similar to those produced in fast pyrolysis reactors.

TABLE 1 Hot Water Hot Water + Oven Original Douglas Fir PretreatmentPretreatment Bio-oil 55.4 ± 4.6 57.1 ± 1.1 56.8 ± 3.6 Char 22.7 ± 5.017.4 ± 0.5 19.5 ± 4.8 Gas 21.7 ± 0.6 25.5 ± 1.6 23.7 ± 1.3

Production of ethanol from pyrolytic sugars was also investigated. Twobio-oils were used to produce ethanol. The first bio-oil produced from ahardwood provided by Dynamotive. The second bio-oil studied was producedin a fast pyrolysis reactor at Monash University (Australia) using as afeedstock a softwood bark. The name and the content of each of thespecies quantified by GC/MS and by Karl Fischer Titration are listed inTable 2.

TABLE 2 Softwood Bark Dynamotive Compound Oil (Monash) Oil 1 Water 13.9229.35 2 Glycolaldehyde 1.41 1.62 3 Acetic Acid 1.17 3.30 4 Acetol 1.562.67 5 Toluene 0.003 0.001 6 Cyclopentanone 0 0.002 7 2-Furaldehyde 00.52 8 2-Cyclopenten-1-one, 2-methyl- 0 0.04 9 2(5H)-Furanone 0 0.36 102-Furanethanol, b-methoxy-(S)- 0.35 0.83 11 Phenol 0.58 0.29 12 O-Cresol0.28 0.14 13 p-Cresol and m-Cresol 0.55 0.18 14 Phenol, 2-methoxy- 1.811.07 15 Phenol, 2,4-dimethyl- and 0.31 0.12 Phenol, 2,5-dimethyl- 16Phenol, 4-ethyl- 0.26 0.08 17 Phenol, 3,4-dimethyl- 0.22 0 18 Phenol,2-methoxy-4-methyl- 0.80 0.29 19 Pyrotechol 1.14 0.67 201,2-Benzenediol, 3-methyl- 0.71 0 21 Phenol, 4-ethyl-2-methoxy- 0.430.17 22 1,2-Benzenediol, 4-methyl- 1.56 0 23 Syringol 0 1.11 24 Eugenol0.31 0.13 25 Phenol, 2-methoxy-4-propyl- 0.21 0.09 26 4-Ethylcatechol0.16 0 27 Vanillin 0.45 0.30 28 Phenol, 2-methoxy-4-(1- 0.76 0.05propenyl)-, (E)- 29 1,6-Anhydro-b-D-Glucose 3.61 4.07 30 2-Propanone,1-(4-hydroxy-3- 0.52 0 methoxyphenyl)- 31 Syringaldehyde 0 0.50 32Phenanthrene, 1-methyl-7- 0.003 0 (1-methylethyl)- Total 33.09 47.9

As shown in Table 2, the softwood bark derived oil produced at Monashcontains significantly less water than the oil provided by Dynamotive.The content of phenols in the softwood bark derived oil is higher thanin the oil provided by Dynamotive.

Table 3 shows the content of sugars in the oil produced by Dynamotive.The glucose quantified in this oil was derived from the hydrolysis oflevoglucosan, cellobiosan and other oligo-anhydrosugars. The content ofglucose (a fermentable sugar) in these oils is approximately 5.02 mass%. This concentration of sugar is suitable for fermentation. The othersugars derived from hemicelluloses (fucose, arabinose, galactose,mannose/xylose, fructose, ribose) accounted for 1.08 mass % of this oil.

TABLE 3 Sugars Content (mass %) Fucose 0.058 Arabinose 0.105 Galactose0.197 Glucose 5.028 Mannose/Xylose 0.586 Fructose 0.115 Ribose 0.019Total sugars 6.108

Although the bulk of the phenolic compounds from bio-oil can beextracted with the ethyl acetate, small concentrations of these toxiccompounds remain in the aqueous phase together with most of the sugars.The nature and the range of lethal concentrations of many of these toxiccompounds was not well known. Thus, we carried out tests with modelcompounds to identify which of them were toxic to yeasts.

The toxic effects of selected bio-oil compounds (acetic acid, propanoicacid, cyclopentanone, 2-furaldehyde, furfuryl alcohol, phenol, eugenol,acetol, 2-(5H)-furanone, stilbene, vanillin, syringaldehyde, o-cresol)on Saccharomyces cerevisiae were studied. The concentration of each ofthe compounds tested was 25, 50, 75 and 100% of the concentration foundin bio-oils (CFBO) for a fast pyrolysis oil derived from Mallee whichwas produced at a pyrolysis temperature of 500° C. The inhibition rateestimated for the compounds studies is shown in Table 4.

TABLE 4 25% of 50% of 75% of 100% of N^(o) Compound CFBO CFBO CFBO CFBO1 Acetic acid 97.75 97.75 97.96 98.24 2 Propanoic acid 97.01 97.54 97.8298.00 3 Cyclopentanone −22.07 −5.26 −4.41 21.73 4 2-furaldehyde 7.817.98 11.03 95.89 5 Furfuryl alcohol 5.94 6.90 7.81 7.81 6 Phenol 76.9596.95 97.45 97.67 7 Eugenol 97.04 97.22 96.64 97.04 8 Acetol 44.17 77.8078.93 80.07 9 2-(5H)-Furanone 3.057 5.89 8.83 10.42 10 Stilbene 9.1732.62 37.89 45.07 11 Vanillin 81.54 82.45 81.77 81.88 12 Syringaldehyde71.68 79.95 81.54 81.99 13 O-cresol 2.61 14.16 23.38 31.22 14 O-xylol5.01 5.23 5.33 5.44 15 Pyrocatechol 84.53 90.48 91.67 92.10 16 Palmiticacid 2.63 0.36 −2.02 −4.19 17 Toluene −0.72 1.00 1.66 2.09 18Tetradecane 1.11 4.68 10.53 10.64 19 Petadecane 4.68 7.39 8.90 9.78

As shown in Table 4, the carboxylic acids (acetic acid and propanoicacid) and the phenols (phenol, eugenol, vanillin, syringaldehyde,pyrocatechol) are the most lethal compounds inhibiting yeast growth. Thefurans (furaldehyde, furfuryl alcohol, 2-(5H)-furanone) and the alkanes(tetradecane, pentadecane) are also inhibitors but their inhibition rateis much lower.

Extraction of phenols, hydrolysis, detoxification and fermentation ofpyrolytic sugars were also tested. Ethyl-acetate was the solvent usedfor the extraction of compounds from the bio-oil. The method employed toseparate the phenols is similar to the one patented by NREL for theproduction of resins. Briefly, blends of ethyl acetate/bio-oil with massratio of 1:1 were prepared. The blends were shaken for 10 minutes at 30°C. and were left to equilibrate for over 6 hours. The organic phase richin ethyl acetate which contains most of the phenols was separated bydecantation and the ethyl acetate solubilised in the aqueous phaseremoved with a rotary evaporator at 80° C.

The sugars in the aqueous phase (levoglucosan, cellobionsan) werehydrolysed using H₂SO₄ as catalyst to produce glucose. The phenolsremaining in the aqueous phase were removed by adsorption on activatedcarbon. An activated carbon/aqueous solution volume ratio of 1:1 wasemployed. The aqueous solution was left overnight at 4° C. in therefrigerator and the slurry formed was filtrated to obtain a colorlessliquid. The aqueous solution containing the sugars was then neutralizedto pH 7 with solid barium hydroxide. Under these conditions the freesulfuric acid and the acetic acid present in the aqueous phase areremoved as precipitated salts.

The content of sugars in the detoxified solution was quantified by IonExchange Chromatography and the detoxified aqueous phase rich in sugarswas then fermented. Briefly, YPD media was prepared by taking 25 ml ofthe detoxified solution obtained in the previous step, 2 mass % yeastextract and 1% mass peptone. 10 vol of Saccharomyces cerevisiae seedculture media was then inoculated in the YPD media. The media wascultured at 30° C. and the micro-organism growth, sugar consumption andethanol production were monitored by UV-Vis, ion exchangechromatography, and GC-FID. The initial content of glucose in thedetoxified aqueous phases from the Dynamotive oil and from the oilproduced in Monash University were 2.6 and 2.0 mass % respectively.Clearly the solvent extraction method should be further improved.Control solutions containing the same concentrations of glucose werealso fermented.

FIG. 10 shows a glucose content as a function of fermentation time.Based on the consumption of glucose it appears that the fermentationprocess happened mainly during the first 5 hours. No major differencewas observed between the behavior of the control and the solutionsderived from pyrolysis oils.

FIG. 11 shows a rate of microbial growth in solutions derived frombio-oils and in control solutions produced with glucose. As shown inFIG. 11, most of the growth happened in the first 5 hours and that thegrowth in the solution derived from bio-oil was comparable with thegrowth obtained with the control solution prepared with glucose. Verylittle microbial growth was observed after the first 5 hours.

FIG. 12 shows ethanol concentration as a function of fermentation time.High concentrations of ethanol were produced (12-16 g/L) during thefirst 5 hours. The production of ethanol slowed down after almost thesame time that the content of glucose in the solution was depleted. Theproduction of ethanol from the solutions derived from bio-oils wascomparable to the production of ethanol from the control. The effect ofany inhibitor remaining in the solution was negligible.

Fatty acids were produced from glucose using oleaginous yeasts(Cryptococcus curvatus and Rhodotorula glutinis yeasts). These yeastswere cultured for periods varying between 24 and 144 hours on a mixturerich in xylose and glucose which were derived from pyrolysis oils. Theinitial content of glucose in the solution was 6.8 mass %.

FIG. 13 shows sugar consumption and production of fatty acids as afunction of fermentation time in accordance with embodiments of thetechnology. Microorganisms with fat content ranging from 28 to 68 mass %were obtained with the Cryptococcus curvatus. Lower fat contents(between 13 and 45 mass %) were obtained with Rhodotorula glutinis. Themost important fatty acids found in Cryptococcus curvatus were: palmitic(C16:O) (20 mass %), stearic (C18:O) (20 mass %) and oleic (48 mass %)acids. A slightly different fatty acid profile was observed for theRhodotorula glutinis: palmitic (15 mass %), stearic (20 mass %) andoleoic: (51 mass %).

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thetechnology. Many of the elements of one embodiment may be combined withother embodiments in addition to or in lieu of the elements of the otherembodiments. Accordingly, the technology is not limited except as by theappended claims.

1. A process for processing a biomass, comprising: treating a biomass byheating the biomass at a first temperature; thermally converting thetreated biomass into a product having an oil portion and an aqueousportion via pyrolysis at a second temperature, the first temperaturebeing lower than the second temperature; and selecting the firsttemperature based on a correlation between the first temperature and adesired anhydrosugar content in the oil portion of the product.
 2. Theprocess of claim 1 wherein thermally converting includes using asynthesis gas as a carrier gas in a pyrolysis reactor.
 3. The process ofclaim 1, further comprising producing an oil phase in a first condenserand producing an aqueous phase in a second condenser, the first andsecond condensers are in a series.
 4. The process of claim 1, furthercomprising separating sugars from phenols in the oil phase vialiquid-liquid extraction with a solvent.
 5. The process of claim 1,further comprising converting at least a fraction of sugars in the oilphase to ethanol.
 6. The process of claim 1 wherein the oil phasecontains sugars, and wherein the process further comprising convertingat least a fraction of the sugars into lipids.
 7. The process of claim 1wherein treating a biomass includes treating a biomass by heating thebiomass at a first temperature of about 200° C. to about 300° C.
 8. Theprocess of claim 1 wherein treating a biomass includes treating abiomass by heating the biomass at a first temperature of about 200° C.to about 300° C. for a period of time of about 3 minutes to about 10hours.
 9. The process of claim 1 wherein treating a biomass includestreating a biomass by heating the biomass at a first temperature ofabout 200° C. to about 300° C. for a period of time of about 1 minutesto about 10 hours, and wherein the first temperature is inverselyrelated to the period of time.
 10. A process for processing a biomass,comprising: providing a biomass having a first crystallinity; modifyinga structure of cellulose in the biomass to have a second crystallinityhigher than the first crystallinity; and thermally converting thebiomass with the increased crystallinity into a pyrolysis productcontaining anhydrosugar via pyrolysis.
 11. The process of claim 10wherein: the first crystallinity of the biomass corresponds to a firstanhydrosugar content of the pyrolysis product; and modifying thestructure of cellulose includes modifying the structure of cellulose tohave a second crystallinity and/or a degree of polymerizationcorresponding to a second anhydrosugar content higher than the firstanhydrosugar content of the pyrolysis product.
 12. The process of claim10 wherein: the first crystallinity of the biomass corresponds to ananhydrosugar content of the pyrolysis product; and modifying thestructure of cellulose includes enhancing the anhydrosugar content ofthe pyrolysis product.
 13. The process of claim 10 wherein modifying thestructure of cellulose includes heating the biomass at a firsttemperature of about 200° C. to about 300° C.
 14. The process of claim10 wherein modifying the structure of cellulose includes heating thebiomass at a first temperature of about 200° C. to about 300° C. for aperiod of time of about 1 minute to about 10 hours.
 15. The process ofclaim 10 wherein modifying the structure of cellulose includes heatingthe biomass at a first temperature of about 200° C. to about 300° C. fora period of time of about 3 minutes to about 10 hours, and wherein thefirst temperature is inversely related to the period of time.
 16. Aprocess for processing a biomass, comprising: heating a biomass at afirst temperature; thermally converting the heated biomass into aproduct via pyrolysis at a second temperature, the first temperaturebeing lower than the second temperature; and wherein the firsttemperature is selected to enhance an anhydrosugar content in theproduct from thermally converting the heated biomass.
 17. The process ofclaim 16 wherein the first temperature is selected to be about 200° C.to about 300° C.
 18. The process of claim 16 wherein the firsttemperature is selected to be about 200° C. to about 300° C., andwherein a heating period of time is also selected to enhance theanhydrosugar content in the product from thermally converting the heatedbiomass.
 19. The process of claim 16 wherein the first temperature isselected to be about 200° C. to about 300° C., and wherein a heatingperiod of time is also selected to enhance the anhydrosugar content inthe product from thermally converting the heated biomass, the heatingperiod of time being about 1 minute to about 10 hours.
 20. The processof claim 16 wherein the first temperature is selected to be about 200°C. to about 300° C., and wherein a heating period of time is alsoselected to enhance the anhydrosugar content in the product fromthermally converting the heated biomass, the heating period of timebeing about 1 minutes to about 10 hours and inversely related to thefirst temperature.